1. Field of the Invention
The present invention relates generally to a telecommunications system and method for improved location updating and paging, particularly, to a telecommunications system and method for improved location updating and paging of subscribers within a single-, dual- or multi-mode telecommunications system.
2. Background and Objects of the Present Invention
The evolution of wireless communication over the past century, since Guglielmo Marconi's 1897 demonstration of radio's ability to provide continuous contact with ships sailing the English Channel, has been remarkable. Since Marconi's discovery, new wireline and wireless communication methods, services and standards have been adopted by people throughout the world. This evolution has been accelerating, particularly over the last ten years, during which the mobile radio communications industry has grown by orders of magnitude, fueled by numerous technological advances that have made portable radio equipment smaller, cheaper and more reliable. The exponential growth of mobile telephony will continue to rise in the coming decades as well, as this wireless network interacts with and eventually overtakes the existing wireline networks.
Numerous telecommunications systems have been designed to implement wireless telephony, e.g., the Advanced Mobile Phone Service (AMPS) cellular system in the United States, the Nordic Mobile Telephone (NMT) system in Northern Europe, and more recently the Global System for Mobile Communications (GSM) and DCS 1800 digital systems. All of the above systems are terrestrial systems, i.e., having earth-based as opposed to satellite-based transmissions.
The Association of SouthEast Asian Nation's (ASEAN) Cellular Satellite (ACeS) system is such a satellite-based Digital Mobile Satellite (DMS) system providing telephone coverage by use of a geo-stationary satellite. Although still in the specification stage, ACeS is essentially an adaption of the popular GSM specification. Expected to be deployed over SouthEast Asia, ACeS would provide coverage to areas having limited land-line and cellular infrastructures, allowing use of hand-held pocket phones across Asia. When deployed, the satellite footprint of the ACeS system will allow service from India to Japan and from Northern China to Indonesia using a large number of spot beams.
In geographical areas covered by both an earth-based and by a satellite-based system, the subscribers to a terrestrial system, such as GSM, and a satellite system, such as ACeS, may need to switch to the other "mode" of transmission. Accordingly, the subscribers' mobile phones need to have dual-mode capability to operate in and switch between the two modes of the two systems. For example, in a satellite-based system such as ACeS, the mobile unit may be taken into a large building or other structure or tunnel which interferes with or blocks satellite communication. If it is a dual-mode device, the mobile phone can detect a signal interference problem and automatically switch to the terrestrial system offering a better signal. Conversely, a GSM user may switch to ACeS in those areas, e.g., undeveloped areas, with poor infrastructures to support GSM transmissions. Interworking pairs of terrestrial-based and satellite-based systems, such as GSM and ACeS, advantageously offer such dual-mode capability. A problem has arisen, however, in the interworking between these diverse systems as a result of the attempts by ACeS' designers to adhere to GSM standards.
One of these problems is that upon transfer from one system to the other, e.g., from ACeS to GSM, the GSM system does not handle the subscription record of the ACeS subscriber any differently than that of a GSM subscriber. Thus, instead of distinguishing the visiting mobile user as a non-GSM user, the GSM system treats the visiting ACeS subscriber and their mobile registration information as an extension of the GSM system, and, in accordance with GSM protocol, location update information is transmitted back to the ACeS system, overwriting the mobile registration therein with GSM location information. Since the ACeS registration information has been deleted, upon return of the mobile from GSM to ACeS, re-registration in the ACeS system is necessary with the requisite exchange of information between the mobile and other earth-based equipment through the orbiting satellite, causing delay and increased signal traffic within ACeS. Such generated location update traffic, however, has the capacity to exceed the estimated signaling capability of the ACeS network, and would place a serious load on the whole system. If, alternatively, location update traffic is restricted, the mobiles would then be out of reach and the paging performance of the ACeS or other such satellite network poor.
This problem is exacerbated by the fact that GSM is an established system, making any modifications thereto difficult, unconventional and costly. Since DMS systems, such as ACeS, are still in the specification and development stage, however, solutions to this and other interworking problems are better handled by modifications to these presently more flexibly defined DMS systems.
Additionally, because of the aforementioned communications difficulties within DMS systems, subscribers in single-mode systems such as ACeS may encounter the same problems along location or service area borders within ACeS, whereby excessive non-speech over-the-air traffic may overload the system.
Accordingly, it is an object of the present invention to modify DMS systems, such as the presently developed ACeS system, to ameliorate or overcome the aforedescribed signal traffic problems caused by increased location updates.
It is an additional object of the present invention to modify DMS systems, such as ACeS, to decrease location updates by maintaining a second location address of an ACeS subscriber, where the home location or service area of the subscriber is preserved while the subscriber visits another location or service area within the DMS or other system where non-speech over-the-air traffic must be limited.
It is a further object of the present invention to decrease location updates by maintaining dual location addresses of a subscriber in a dual-mode telecommunications system, such as a satellite-based ACeS and earth-based GSM pair, where the home address of the subscriber in their home system is preserved while the subscriber visits the other system.